The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a functional block diagram of an engine system 100 is presented. The engine system 100 includes an engine 102 that may be used to produce power by combusting fuel in the presence of air. Typically, air is drawn into the engine 102 through an intake manifold 104. A throttle valve 106 may be used to vary the volume of air drawn into the intake manifold 104. The air mixes with fuel that may be dispensed by one or more fuel injectors 108 to form an air and fuel (A/F) mixture. The A/F mixture is combusted within one or more cylinders of the engine 102, such as cylinder 110. Combustion of the A/F mixture may be initiated by spark provided by a spark plug 112. Exhaust gas produced during combustion may be expelled from the cylinders to an exhaust system 114.
The exhaust system 114 may include one or more oxygen sensors, such as oxygen sensor 116, that may be used to measure the amount of oxygen in the exhaust gas. The oxygen sensor 116 may be threaded into a hole provided in the exhaust system 114 and thereby be disposed within a flow of the exhaust gas. The oxygen sensor may output a voltage corresponding to the quantity of oxygen in the exhaust gas. It may be desired to operate the oxygen sensor 116 above a particular temperature, such as a sensitivity temperature, in order to ensure a reliable output voltage. Accordingly, the oxygen sensor 116 may include a heater that receives power from a heater power supply 118. The heater may be used to supply supplemental heat and thereby bias the oxygen sensor 116 to within an operating temperature range above the sensitivity temperature.
An engine control module (ECM) 120 may be used to regulate the operation of the engine system 100. The ECM 120 may receive the output voltage of the oxygen sensor 116, along with signals from other sensors 122. The other sensors 122 may include, for example, a manifold absolute pressure (MAP) sensor and an intake air temperature (IAT) sensor. Based on the output voltage of the oxygen sensor 116, the ECM 120 may regulate the A/F mixture by regulating the throttle valve 106 and fuel injectors 108. The ECM 120 may also regulate the A/F mixture based on the signals it receives from the other sensors 122.
The temperature of the oxygen sensor 116 may be below the sensitivity temperature when the engine 102 is started. Accordingly, the output voltage of the oxygen sensor 116 may be unreliable for a period of time after engine startup. While the output voltage of the oxygen sensor 116 is deemed unreliable, the ECM 120 may regulate the A/F mixture independent of the output voltage of the oxygen sensor 116.
Heat provided by the exhaust gas and the heater may be used to bring the temperature of the oxygen sensor 116 above the sensitivity temperature. However, for a period of time after engine startup, water condensate present within the exhaust system 114 may become entrained in the exhaust gas come in contact with the oxygen sensor 116. Liquid water that comes into contact with the oxygen sensor 116 may cause thermal shock to the oxygen sensor 116. Repeated thermal shock to the oxygen sensor 116 may induce fractures in the oxygen sensor 116 and result in premature failure.